1. Field of the Invention
The present invention relates to a developing member which is incorporated in an apparatus adopting an electrophotographic system, such as a receiving apparatus of a copier, a printer, or a facsimile, and is used while it is in contact with or close to a photosensitive member. Moreover, the present invention relates to a process cartridge and an electrophotographic apparatus.
2. Description of the Related Art
In a copier, a facsimile, or a printer adopting an electrophotographic system, a photosensitive member is charged electrically by a charging unit and an electrostatic latent image is formed by means of a laser. Next, a toner in a developer container is applied on a developing member by a toner feeding roller and a toner control member, and development by the toner is performed at a contact or closed part between the photosensitive member and the developing member. After that, the toner on the photosensitive member is transferred to a sheet of recording paper by a transferring unit and is fixed by the action of heat and pressure, and the remaining toner on the photosensitive member is then removed by a cleaning blade.
In order to charge the photosensitive member and develop the electrostatic latent image, an elastic member having electric resistance of 103 to 1010 Ω·cm is used for an image forming apparatus of non-magnetic one-component contact developing system. In this system, an electrostatic latent image is developed in such a way that a toner is moved to an electrophotographic photosensitive member (drum) from a developing member, which are in contact with each other by the action of pressure, and eventually, a toner image is formed.
In recent years, performance required for a developing member used in an apparatus adopting an electrophotographic system has been advanced. From the viewpoint of high image quality and high durability, a two-layer developing member in which a surface layer is provided on a surface of an elastic layer has been commonly used.
A surface layer containing a urethane resin having high abrasion resistance and being capable of providing a charge imparting property to a toner has become popular. Furthermore, recently, in order to obtain higher functionality in a charging member, a method for improving a surface layer has been proposed.
Japanese Patent Application Laid-Open No. 2004-339253 discloses that abrasion resistance and sliding properties are improved by incorporating an acrylic resin in a urethane resin.
Moreover, Japanese Patent Application Laid-Open No. 2008-139482 discloses that toner adhesion in a high-temperature and high-humidity environment is suppressed by incorporating an acrylic resin having predetermined physical properties in a polyether-based urethane resin.